UHF CB compatibility with new 80 channel radios
Submitted: Saturday, Feb 26, 2011 at 16:00
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Mike DiD
In the next six months UHF CBs with new channels will appear on the market. They won't actually have 80 channels, because 5 are reserved for Telemetry (22,23) or future use (61,62,63).
You can now buy 40 channel sets which can be upgraded to the new 80 channel standard when it becomes legal to use the new 75 channels.
It will be legal to keep on using existing 40 channel radios for at least the next 5 years.
You will be able to use 40 channel radios to talk to 80 channel radios, but -
- listening on a 40 channel radio to transmissions from an 80 channel radio will give much quieter audio level.
- listening on an 80 channel radio to transmissions from a 40 channel radio will give distorted audio, unless you get them to speak quietly !
Listening on a 40 channel radio, you will get interference from people operating on the new channels. e.g. if you're listening on 20 you will get interference from people transmitting on 59 and 60.
It will still be legal to sell 40 channel for a while - one Australian manufacturer has said they can change all models to 80 channels within 12 months. One importer has said they need three years to change all models !!!
Reply By: Mike DiD - Saturday, Feb 26, 2011 at 16:12
Saturday, Feb 26, 2011 at 16:12
When considering radios that can be upgraded to the new 80 channel plan, keep in mind that there are two levels of compatibility that are technically possible.
1. Narrowband receive - the new standard requires receivers to have better selectivity - if listening on 20, it must not pick up signals on adjacent channels 59 or 60. This cannot be done with sets that were only designed for 25kHz channel spacing, even though they may have the addition 35 channels programmed in.
2. Wideband receive - existing 40 channel CBs or commercial radios only designed for 25kHz channel spacing may be able to have the additional 35 channels programmed in, but they will have the same problem of adjacent channel interference e.g. if you're listening on 20 you will get interference from people transmitting on 59 and 60.
When buying a radio that promises upgradability to the new channels, be sure to
check if it has the narrowband selectivity for 12,5 kHz channel spacing !
All radios designed specifically for the new 80 channel plan, must have Narrowband receive.
AnswerID:
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Reply By: Member - Tezza Qld - Saturday, Feb 26, 2011 at 16:35
Saturday, Feb 26, 2011 at 16:35
Hi Mike
We have done some testing with these channels and whilst some small interference was noted on the 40 channel set tuned to channel 20 for instance, and channels 59 or 60 were used to transmit, but it seemed to be a matter of how close the radios were together.
We used a GME 3440 as the 40 channel unit and 2 icom 400,s for the 80 channel units. Interestingly was when one Icom was used as a 40 channel set, and the other as an 80 channel set, no interference at all was found between the Icoms.
I think that the levels or audio between radios is going to be related to the distance of tranmission and the out put of the radio. As we know the aerial has some bearing on this.
Will be interesting when it all comes into place. Our testing was purely for our own benifit as a Tour operator , to shortcut any problems we may face with communications during tours by some people using new radios and some using the older ones.
Cheers Teza
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Follow Up By: Mike DiD - Saturday, Feb 26, 2011 at 16:39
Saturday, Feb 26, 2011 at 16:39
I would expect the IC400s to have filters with steeper skirts than the GMEs.
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Follow Up By: Nomadic Navara - Saturday, Feb 26, 2011 at 21:44
Saturday, Feb 26, 2011 at 21:44
Quote - "I think that the levels or audio between radios is going to be related to the distance of tranmission and the out put of the radio. As we know the aerial has some bearing on this."
Not so, UHF CB has FM modulation. The effect you are referring to only happens on AM.
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Reply By: Mike DiD - Saturday, Feb 26, 2011 at 20:45
Saturday, Feb 26, 2011 at 20:45
From Manufacturer/Importer websites -
GME
- "As from December 2010 production onwards, a number of our current 40 channel wideband radios will be able to be upgraded to the new 80 channel narrowband standard. These radios are easily identifiable by the upgradeable sticker on the packaging and by the serial number with the prefix 012, 101, 102 and103. All radios with the serial number of 011 (November 2010) or earlier are not user or dealer upgradeable via software.
The TX3100 and TX3340 will be User upgradeable, while the TX3220, TX3420 and TX3440 will be Dealer upgradeable"
UNIDEN
- " The UH7760NB (also UH7700NB) is 77 Channel Ready* making it one of the first UHF mobiles in the market available and user upgradeable for free when the ACMA standard is published early in the year."
- ". The built-in AVS circuitry allows for an automatic volume stabiliser detecting narrowband and wideband transmission automatically adjusting incoming audio to comparable levels."
Note that the current draft standard only provides for 75 voice channels, so UNIDEN will have to change this to make their sets legal.
ICOM
- we'll have to change our radios ???
AnswerID:
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Follow Up By: Isuzumu - Saturday, Feb 26, 2011 at 21:33
Saturday, Feb 26, 2011 at 21:33
Is there going to be benefits with the the new 80 ch radios, like better transmitting distance or will we just be getting more channels? letting more idiots broadcast on more frequencies seems all a bit pointless really to me
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